Many flotation vest constructions are known in the prior art, and the following patents are exemplary:
U.S. Pat. No. 4,167,051, Galecke, Sept. 11, 1979; PA0 U.S. Pat. No. 3,540,067, Deruaz, Nov. 17, 1970; PA0 U.S. Pat. No. 3,545,017, Cohn, Dec. 8, 1970. PA0 U.S. Pat. No. 4,047,255 issued Sept. 1977 to Kiefer PA0 U.S. Pat. No. 3,545,017 issued Dec. 1970 to Cohn PA0 U.S. Pat. No. 4,316,286 issued Feb. 1982 to Klein PA0 U.S. Pat. No. 3,323,151 issued June 1967 to Lerman PA0 U.S. Pat. No. 4,281,428 issued Aug. 1981 to Rochlin PA0 U.S. Pat. No. 4,380,441 issued April 1983 to Harr PA0 U.S. Pat. No. 2,029,394 issued Feb. 1936 to Sidebotham PA0 U.S. Pat. No. 3,434,399 issued March 1969 to Palmer.
All of these vest constructions are acceptable in terms of function, but the complexity of the stitch-lines, the plurality of the pockets, or the requirement for large sheets of buoyant material with complicated outlines, renders these prior art devices costly to produce, and therefore not competitive in the marketplace.
In terms of the economies of manufacturing flotation vests, it is important to understand that there are currently two kinds of foamed plastic which are generally utilized. The more expensive of these is PVC foam, which is relatively soft at a thickness of 1 inch, and can be used in that thickness to provide buoyant inserts for vests. A less expensive material is polyethylene foam, but it is substantially stiffer and more rigid than PVC foam. The polyethylene foam typically comes in boards or sheets of 1/4 inch thickness. At the thickness of 1/4 inch, the polyethylene foam is flexible enough to be utilized in vests, but if only 1/4 inch were provided, there would be insufficient buoyancy to meet regulations. Because of this, economy-minded manufacturers utilize a plurality of such sheets juxtaposed against each other, typically four sheets in a pocket giving an overall thickness of 1 inch.
In a particularly simple vest construction, a roughly rectangular back panel is joined along its lower side edges to two front panels which meet at the centre to provide a zipper connection. Lapel portions extend upwardly and outwardly from the inner upper corners of the front panels to meet the upper outer corners of the back panel.
While it would be possible to provide four identical sheets of 1/4 inch polyethylene foam juxtaposed against each other in each of the pockets of the front panels, with the sheets cut in such a way as to provide flotation in the front panels and also up along the lapel portions, the odd shape of each of these panels would be very wasteful of material, and the economy-minded manufacturer would not wish to proceed along these lines.
If it should be conceived to provide separate inserts for the front panel and for the lapel portion, problems of loss of position would be encountered, which will be explained more fully in the description portion of this disclosure.
Further prior art of interest is the following: